In the fabrication of devices such as solar photovoltaic cells and organic light emitting devices (‘OLED’) of a typical planar sandwich construction including a transparent conductor; active material and a rear conductor, it is known that any defect in the structure will severely affect the overall performance of that device. This leads to fabrication procedures needing to be restricted to clean and very clean areas and to coating processes that in themselves are highly defined in terms of coating uniformity and their effect upon other layers in the traditional growing planar sandwich construction typically of thin film solar devices. This reduces the process yields and throughputs as the materials deposited must be very uniform which requires the processing to be very controlled.
It has been found desirable to use roll to roll systems for fabricating electronic devices as the processing speeds can be high and thus the costs can be minimised. However because of the necessarily high speed deposition processes involved the devices produced can be prone to occasional material defects such as pin holes and material spits. It is apparent that if a system could be developed that was insensitive to such material defects then previously unattainable fabrication throughputs and cost reductions could be delivered.
Traditionally thin film optical devices have involved the use of transparent electrical conductors normally zinc oxide or indium oxide based. These conductors generally require higher temperature deposition to achieve the performance needed for commercial products. This requirement can amount to some 30% of the total cost of the device fabrication. This inevitably limits the type of substrate used to one that can withstand the temperature required for the deposition of the transparent conductor and this along with the cost of the transparent conductor set limits for the cost of any device employing same.